1. Field of the Invention
The present invention relates to an optical apparatus having a light-attenuating device and a light-exclusion device assembled therein, and a structure of a camera having the optical apparatus further to a shutter device (optical device) having an exposure opening for passing photographing light therethrough, and a structure of a camera having the shutter device.
2. Related Art Statement
In a conventional optical system of an image-pickup apparatus such as a digital camera, there is a system having a light-attenuating filter (light-attenuating member) called an ND filter inserted therein. The reason for using the ND filter is as follows. That is, an image-pickup element such as a CCD is used in an electronic image-pickup apparatus; a photographing area of the image-pickup element is considerably smaller than the area of a conventional silver-camera film. Accordingly, a diaphragm opening must be relatively smaller; however, by the limit due to light-diffraction, the diaphragm opening cannot be reduced lower than a predetermined value so as to prevent the resolution to be deteriorated. Then, in the case where an exposure amount is required to considerably decrease for picking up a bright object in the outdoors, the exposure amount is totally reduced by adding the ND filter in addition to a mechanical opening diaphragm.
A light-amount adjusting device (optical device) housed in a lens-barrel and disclosed in Japanese Unexamined Patent Application Publication No. 2000-310803 has two diaphragm blades (light-exclusion members) entering and retracting relative to a photographing opening by rotation and an ND filter (light-attenuating member) such that the two diaphragm blades and the ND filter are rotationally driven about different rotational shafts by two actuators disposed to oppose the blades and the filter with the photographing opening therebetween.
Also, a diaphragm device (optical device) for a taking lens disclosed in Japanese Unexamined Patent Application Publication No. 2000-122109 has two diaphragm blades (light-exclusion members) entering and retracting relative to a photographing opening by sliding movement and an ND filter (light-attenuating member) such that the two diaphragm blades and the ND filter are slid by two actuators disposed with the photographing therebetween.
In any light-amount adjusting device (optical device) for a digital camera or the like disclosed in Japanese Unexamined Patent Application Publication No. 2000-310803 and No. 2000-122109 mentioned above, an actuator for driving the diaphragm blade and an actuator for driving the ND filter are arranged with the photographing opening therebetween, and the diaphragm blade and the ND filter are supported by different shafts rotatably or slidably.
Hitherto, in silver film cameras and digital cameras, the miniaturizing in external size is constantly required to enhance portability. Therefore, it is important to reduce spaces occupied by internal units within a camera. Among the internal units, a shutter device (optical device) mounted in an image pickup optical system is used in digital cameras as well as in silver-film cameras. For example, in digital cameras, during frame-image picking up by an interlace image-pickup element or during image picking up by a progressive image-pickup element, a mechanical shutter is required for preventing a smear.
Since the shutter device shields an optical path by opening and shutting thin blades, the size of the shutter device in the thickness direction (optical axial direction) is sufficiently small. Then, it is necessary for miniaturizing the shutter device to reduce the occupied space on a surface orthogonal to the optical axis. One prior art for solving this point, is Japanese Unexamined Patent Application Publication No. 8-313969, for example.
The shutter device (optical device) according to the Japanese Unexamined Patent Application Publication mentioned above incorporates a system in that the number of shutter blades is laterally divided into groups, each with two blades or more, for opening and shutting. In this shutter device, although the number of blades increases, the area of each blade is reduced so that the occupied space on the surface orthogonal to the optical axis is reduced to a size smaller than a conventional shutter device thereby realizing a compact size.
Also, in a shutter device for opening and shutting an exposure opening by operating conventional shutter blades, since the shutter blades are rapidly stopped when the blades reach the opened position or the shut position after the rotation (movement) at high speed, rebounding is liable to occur. The rebounding of the shutter blade non-preferably causes changes in exposure amount or light leakage. Then, various shutter devices, each having a rebound preventing mechanism of the shutter blade, have been proposed.
In a focal plane shutter disclosed in Japanese Unexamined Patent Application Publication No. 9-5831, there is provided an elastic buffer member for abutting a blade when a trailing slit blade or a leading slit blade (shutter blade) are driven to an exposure-start position or an exposure-completion position. The rebound of the slit blade at the terminal position is suppressed by the abutment of the elastic buffer member with the slit blade moving at high speed.
A magnetic drive shutter disclosed in Japanese Patent Publication No. 2627904 has a rotator housing a permanent magnet rotationally driven by an electromagnet as a driving source of shutter blades, so that the shutter blades are rotationally driven to the opened position or the shut position via the rotator. If the electromagnet is electrically turned on, the shutter blades are rotationally driven to the opened position. If the electromagnet is turned off, the shutter blades are rotationally driven to the shut position; at this time, the rotator abuts the elastic buffer member arranged at the rotation terminal position. The rebounding of the rotator is reduced at the terminal position by the abutment with the elastic buffer member so as to suppress the rebound of the shutter blades.
Furthermore, a rebound-preventing control device disclosed in Japanese Utility Model Registration No. 62-3792 is a control device applicable to a high-speed drive device, such as shutter blades of a camera, including a substrate having an exposure opening and shutter opening/closing plates slidably supported on the substrate. The shutter opening/closing plates are driven from one terminal position to the other terminal position by an abutting force of a charge spring corresponding to the operation of the electromagnet for opening and shutting the exposure opening of the substrate. When the plates reach the terminal position, a projected engaging member provided in the shutter opening/closing plates abuts the upper surface of the elastic buffer member so as to elastically deform the elastic buffer member. By the elastic deformation of the elastic buffer member, a braking force is applied to the shutter opening/closing plates so as to suppress the bound at the terminal position.